Institute of Genetics, Academia Sinica, Beijing, China.
Theor Appl Genet. 1985 Aug;70(5):529-35. doi: 10.1007/BF00305986.
Two 30 μg/ml BrdU-resistant sublines and two 60 μg/ml BrdU-resistant sublines are induced from a Chinese hamster cell line Wg3h (HGPRT(-)) by one-step and two-step selections, respectively. By inoculating the cells into BrdU-free medium or by adding more BrdU into the culture medium for 26-27 h, it was found that the two BrdU-resistant sublines analysed have very clear sister chromatid differential (SCD) staining patterns. This indicates that some of the nuclear DNA of the BrdU-resistant cells incorporate with BrdU to reach a kinetic balance. Frequencies of sister chromatid exchange (SCE) of the resistant cells are twice to four times as high as those of the Wg3h cells, depending on which BrdU-resistant subline is analysed. The SCE frequencies of the resistant cells also increase with the BrdU concentration in the medium. Analysis of silver-stained nucleolar organizer regions (NORs) indicates that the NOR activity of three out of the four BrdU-resistant sublines is significantly suppressed, i.e., averages of the Ag-NOR number and number of the chromosomes bearing Ag-NORs per cell decrease significantly. The degree of suppression for different BrdU-resistant sublines may be quite different. The suppressed NOR activity of the resistant cells can gradually be restored when the cells are inoculated into BrdU-free medium, but the recovery speed is far lower than that of the Wg3h cells. The suppression of the NOR activity of the BrdU-resistant sublines should be due to BrdU toxicity.
通过一步法和两步法选择，分别从中国仓鼠细胞系 Wg3h（HGPRT(-)）诱导出两个 30 μg/ml BrdU 抗性亚系和两个 60 μg/ml BrdU 抗性亚系。通过将细胞接种到不含 BrdU 的培养基中或在培养物中添加更多的 BrdU 26-27 h，发现分析的两个 BrdU 抗性亚系具有非常清晰的姐妹染色单体差异（SCD）染色模式。这表明 BrdU 抗性细胞的一些核 DNA 与 BrdU 掺入达到了动力学平衡。抗性细胞的姐妹染色单体交换（SCE）频率是 Wg3h 细胞的两倍到四倍，具体取决于分析的是哪个 BrdU 抗性亚系。抗性细胞的 SCE 频率也随培养基中 BrdU 浓度的增加而增加。银染核仁组织者区域（NORs）的分析表明，四个 BrdU 抗性亚系中的三个 NOR 活性明显受到抑制，即 Ag-NOR 数的平均值和每个细胞携带 Ag-NOR 的染色体数明显减少。不同 BrdU 抗性亚系的抑制程度可能有很大差异。当细胞接种到不含 BrdU 的培养基中时，抗性细胞的 NOR 活性可以逐渐恢复，但恢复速度远低于 Wg3h 细胞。BrdU 抗性亚系 NOR 活性的抑制应归因于 BrdU 毒性。
